1. Field of the Invention
The present invention relates to a holder for holding a tool of the type in which fluid such as cutting oil, coolant, and mist including air and coolant is spouted to a workpiece to be worked through a fluid channel located at the tip end or nearby.
2. Description of the Related Art
When doing cutting process effectively such as boring, it is necessary to supply the portion of the workpiece to be worked with the cutting oil sufficiently. Such tools and tool holders as shown in FIG. 16 are known as such which supplies cutting oil etc. to the workpiece particularly on the portion to be worked from the tip end of the tool through a fluid channel provided inside the tool.
In this prior art, the tool holder portion of the tool holder is constituted from a collet 22, a tip end opening 23a of a quill 23 and a rock nut 24. The collet 22 comprises a tip portion 22a and a rear end 22b both tapered on the outer circumference, and several split grooves are provided in an axial direction of the collet to reduce its diameter. The inner surface of the tip end opening 23a is formed in a tapered manner and the outer circumference thereof is provided with a male screw 23b. The inner surface 24a of the tip of the rock nut 24 is formed in a tapered manner and the inner surface of the rear end is tapped to form a female screw 24b.
A straight shank portion 21b of an oil-through-drill 21 is coupled with the tip end opening 23a of the quill 23 through the collet 22. The rock nut 24 abuts against the tip end 22a of the collet 22 on the inner surface 24a of the tip end, and by a female screw 24b it screws together with male screw 23b. Since the collet 22 and the rock nut 24 abut against the surface 24a of the tip end, in accordance with the screwed amount of the rock nut 24 into the tip end opening 23a of the quill 23, the rear end 22b of the collet 22 is coupled with the inner side of the tip end opening 23a of the quill 23. Since the inner surface of the tip end opening 23a of the quill 23 is formed in a tapered manner, the collet 22 coupled inside is reduced in its diameter by being reduced in the spacing between the grooves of the plurality of split grooves provided in an axial direction.
The straight shank 21b of the oil-through-drill 21 has a diameter identical with the inner diameter or less of the fluid supply hole 23e of the quill 23, which is clamped with the collet 22 along with the reduction of the diameters of the tip end 22a and the rear end 22b of the collet 22, so that the oil-through-drill is fastened inside the fluid supply hole 23e of the quill.
When a tapered shank portion 23c of the quill 23 is coupled with a main shaft 25, the quill 23 is withdrawn inside the main shaft 25 through a pull stud 26 screwed in the female screw 23d and fixed. Since the oil-through-drill 21 has a fluid channel 21c therein and the quill 23 and the pull stud 26 are provided with fluid supply holes 23e and 26a respectively, when the quill 23 is withdrawn inside the main shaft 25 and fixed, a supply tube 27 of the main shaft 25, the fluid supply holes 26, 23e and the fluid channel 21c are in communication with each other and the fluid such as cutting oil is spouted from the tip end 21a of the tool.
When the fluid such as cutting oil is supplied from the supply tube 27 in the main shaft, the pressure of the fluid such as cutting oil is increased, from, for instance, a gap between the fluid supply hole 23e and the straight shank 21b of the oil-through-drill 21 and the gap which belongs to the tool holding elements such as a plurality of split grooves provided on the collet 22, a great amount of cutting oil under increased pressure leaks, so that a given amount of fluid can not be spouted from the tip end 21a.
Further, also, a great amount of the highly pressurized fluid such as cutting oil supplied to the fluid supply hole of the tool holder leaks from the gaps, which may occur between the tools and the collet gap due to the close adhesion malfunction between the constitutional elements of tool holding portion of a tool holder such as between the straight shank 21b of the oil-through-drill 21 and the collet 22 which abuts against the shank 21b or between the collet 22 and the tapered surface of the tip end opening 21a of the quill 23 as a tool holder, so that there may occur a shortage of the fluid to be spouted from the tip end 21a of the tool.
As a tool holder which may prevent such cutting oil from leaking, what uses in a tool holder an oil seal packing to touch the opening for fluid channel of a tool is known as disclosed in Japanese Utility Model laid-open No. Hei 5-16109. This oil seal packing 50 is shown in FIG. 17.
The oil seal packing is configured like a hat, the tip end 50a of which provides an opening 50b. The tip end 50a touches the end of the oil-through-drill 21, and an annular circumferential trailing end 50c adheres to the fluid supply hole 23e. And when the oil seal packing is pressured by the fluid from the hole 23e, the circumference of the trailing end 50c adheres closely to the inner surface of the quill 23 adjacent to the fluid supply hole 23e and the tip end 50a adheres closely to the inner surface of the collet 22 adjacent to the end of the oil-through-drill 21. So that the leak of the fluid from the slit grooves is prevented.
Further, as shown in FIG. 18, there is known a type in which the outer circumference of an oil seal packing 28 and the inner surface of a fluid supply channel 29 are threaded, thereby the mounting position of the oil seal packing 28 can be regulated so as to make the packing to adhere closely to the end 31 of a tool where the fluid channel path is opened.
However, those conventional arts have the following defects.
First, the oil seal packing 50 shown in FIG. 17 is limited in its mounting position due to the collet 22, so that the position of the oil seal packing can not be regulated. Accordingly, when fitting a tool, the end of the tool has to adhere precisely to the oil-seal-packing. Further, before fastening the oil-through-drill 21, if a little fluid leaking occurs and that leaked fluid attaches on the slit grooves of the collet 22, those slits may collect cut chips and some dusts. And when replacing such oil-through-drill 21, it becomes necessary to wash it. In addition, to avoid such collection, some precautions are needed, such as covering the tool with a dust cover to prevent outer things from being adhered.
Further, in the type of packing 28 as shown in FIG. 18, since the mounting position of an oil seal packing can not be regulated after the assembly of a tool to a tool holder, it is necessary to accord the tool end where the fluid channels are opened with the abutting position of the oil seal packing. That is, if a seal member such as oil seal packings is not precisely positioned to and abutted under an appropriate force on a tool end, the fluid leaks from the gap between the seal member and the tool end and is deposited in the space formed by the seal member and the tool holding portion of the tool holder, it flows out excessively from the gaps between the constitutional elements such as the ones between the collet and tool or between the collet and the tool holder. In addition, even if the positioning is carried out successfully, there may remain still such problems as explained in connection with FIG. 17.